Method of manufacturing a thermoset polymer utility vault lid

ABSTRACT

A method of manufacturing a fiber reinforced composite material lid for an utility vault including mixing an unsaturated polyester thermosetting matrix in to a resin paste, compounding the resin paste into a fiber reinforced composite material, maturing the compounded fiber reinforced composite material, cutting the matured compound into a charge pattern, molding the charge pattern in a mold cavity of a heated mold under low pressure to form the lid and cooling and machining the lid. The mold includes a cavity die and a core die having a shear angle for interfacing the core die within the cavity die and a steam pot for heating the cavity die and the core die, wherein the lid is molded between the cavity die and the core die and removed from the mold by a lid ejection mechanism.

FIELD OF THE INVENTION

The invention relates to a thermoset polymer lid or cover and method ofmanufacturing thereof for an underground or grade level vault used invarious underground industries.

BACKGROUND

Underground or buried vaults, pits, chambers or boxes used in theutilities, security and rail line sectors or other industries cancontain co-axial or optical fiber, copper cable as well as gas and powerlines and other conduits, industrial valves, Wi-Fi antennas etc. Vaultsand pits for underground utilities often need to be opened for makingrepairs or for enhancing services. Typically utility vaults and pitsinclude a concrete, polymer concrete, cast iron, galvanized steel orplastic lid which is opened by a tool or pick with a hook at one end.The hook is inserted through a hole in the lid or cover and is used forprying the lid or cover away from its opening atop the vault or pit.

Because underground utility vaults or pits are often times required tobe located in sidewalks, right aways, alley ways and streets or otherhigh traffic areas, the cover must be constructed to withstandsubstantial loads. Consequently current lid or cover construction ismade from concrete, polymer concrete and cast iron in order to withstandthe required loads. These cover materials can withstand substantialloads and have a degree of durability required for use in varioustraffic areas. A drawback of these cover types is that they are quiteheavy, weighing in excess of 100 pounds or more depending upon theparticular application. Consequently, due to their weight, they aredifficult to remove for repair, maintenance or adding additionalservices within the apparatus contained within the utility vault or pit.Heavy covers can cause injury or other back problems to workers duringremoval and reinstallation of the covers.

Utility vault and pit covers are also made of plastic but these havelimited application for use in areas where they are subjected to lessload, i.e. green belt or yard applications. The problem with plasticlids is that because they cannot withstand substantial loads, they havelimited applicability and plastic lids provide less coefficient offriction when wet versus polymer covers. Consequently a need exists fora new utility vault and pit cover design which is light in weight, yetis durable in that it can withstand substantial loads and provideimproved slip resistance over currently available covers.

SUMMARY OF THE INVENTION

The present invention in an embodiment provides an improved utilityvault cover or lid which is manufactured from a fiberglass reinforcedpolymer matrix material producing a reduced weight and increasedstrength cover which is lighter, stronger, has improved UVcharacteristics and slip resistance and is less expensive to manufacturecompared to existing cover designs. The lid or cover is used for vaults,pits, chambers or boxes and for ease of presentation shall all bereferred to herein as a vault. Vaults are used in a number of industriesincluding utility, security, gas and rail, for example, where they areunderground, buried or at grade level.

The fiberglass reinforced polymer matrix (FRPM) material is a fiberreinforced polymer material which consists of an unsaturated polyesterthermosetting resin matrix, glass fiber reinforcement and inorganic ormineral filler. Additional ingredients are low-profile additivesincluding a UV inhibitor, cure initiators, thickeners, process additivesand mold release agents. The formulation undergoes a cross linkingreaction when cured under heat and pressure. The fiber reinforcedpolymer material for the cover will retain its original materialproperties and dimensional accuracy over a broad range of temperatures.The cover is on average fifty percent lighter than concrete and polymerconcrete covers and sixty-five percent lighter than cast iron lids.

The fiber reinforced polymer material is made as a continuous sheetwherein a resin paste is transferred to a doctor box where it isdeposited onto a moving carrier film passing directly beneath. Glassfiber rovings are fed into a rotary cutter above the resin coveredcarrier film. Chopped fibers are randomly deposited onto the resinpaste. A second carrier film is coated with resin paste and is laidresin side down on top of the chopped fibers. The layers are then sentthrough a series of compaction rollers where the glass fibers areconsolidated with the resin paste and the air is removed from the sheet.The fiber reinforced polymer material sheet is kept in a temperatureroom until the desired molding viscosity is reached.

When the polymer material is ready for molding it is cut into pieces ofa predetermined size. The cut pieces are then stacked and assembled intoa charge pattern that is the optimum shape and volume to fill a moldcavity. The mold is then closed and the polymer material is compressed.The mold is held closed for a predetermined amount of time to allow thecover to cure. After curing, the mold is opened and the cover is ejectedfrom the lower mold surface with the use of integral ejector pins. Thecover is allowed to cool to room temperature before any necessarymachining operations. The manufacturing process can be automated throughthe use of robotics.

The manufacturing process includes low pressure molding in combinationwith a mold design which incorporates a steam pot to heat the mold,results in lower mold cost, lower material cost and faster cycle times.The mold design allows for low pressure molding which provides fastercycle times resulting in lower production costs while producing areduced weight and improved performance lid.

The cover consists of an uppermost surface which is flat and in itsinstalled condition on the vault is even with grade. The bottom side ofthe cover or lid has an outer rim with a recessed interior area orcavity. The cavity includes features to allow for the attachment ofaccessories and thru-holes as required. The bottom of the lid hascontinuous support ribs spaced in the cavity to transfer load andminimize deflection under load to the outer rim. The outer rim issupported by the vault, frame or other type of supporting recess. In anembodiment, the ribs are uninterrupted for the span of the cavity to therim to provide strength to the lid.

The uppermost surface of the cover lid has a texture or a surfacecondition created by a pattern of features at different depths. Thechange of depth of the flat surfaces creates a slight protrusion intothe surface to push the glass component of the material away from thesurface creating a resin rich surface. The top surface also has a seriesof bosses having shapes of varying heights to allow for aggressivetransitions in the surface of the lid. These shapes are arranged in apattern to allow for additional edge surfaces to grip moving surfaceswhich may come in contact with the top of the cover. The combination ofthe UV inhibitor, boss design and surface texturing creates improved UVcharacteristics and prevents glass fiber blooming. The elevation of thebosses, spacing and angles, along with the texturing of the surfaceenhances the coefficient of friction of the gripping surface resultingin improved slip resistance.

The cover or lid is designed to allow for installation of either an“L-bolt” or a “thru-bolt” for securing the lid to the vault.Self-latching locking assemblies can also be incorporated. The lid alsoincorporates features to allow for the installation of a pick holeretaining cup for use in removing the lid from the vault.

These and other features of the present invention will be more fullyunderstood by reference to the following detailed description and theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a perspective view of an embodiment of a fiber reinforcedpolymer material utility vault or pit cover or lid of the presentinvention;

FIG. 2 is a diagram of the compounding process for manufacturing thefiberglass reinforced polymer material;

FIG. 3 is a cross-sectional view of the mold for manufacturing the lid;

FIG. 4 is a detail view of the mold of FIG. 3;

FIG. 5 is a detail view of the mold of FIG. 3;

FIG. 6 is a detail view of the mold of FIG. 3;

FIG. 7 is a perspective view of the lid positioned on the utility vault;

FIG. 8 is a perspective view of the bottom surface of the lid;

FIG. 9 is a cross-sectional side view of FIG. 7;

FIG. 10 is a perspective view of an alternative bottom view lid design;

FIG. 11 is a cross-sectional view of FIG. 8;

FIG. 12 is a detail view of the upper surface of the lid;

FIG. 13 is a cross-section detail of the surface of the lid of FIG. 12;

FIG. 14 is a perspective view of the lid;

FIG. 15 is a detail view of an L-bolt attachment for the lid;

FIG. 16 is a detail view of the flange for attachment of the lid;

FIG. 17 is a detail view of a self-latching attachment mechanism for thelid;

FIG. 18 is a detail view of the pick hole retaining cup of the lid; and

FIG. 19 is a schematic illustration of an automated manufacturingprocess.

DETAILED DESCRIPTION

Referring to FIG. 1, an embodiment of the invention is a fiberreinforced polymer material utility vault or pit cover or lid 10consisting of an unsaturated polyester thermosetting resin matrix, glassfiber reinforcement and inorganic or mineral filler. It is to beunderstood that the invention is a lid or cover, and these terms areused interchangeably throughout, for a utility vault or pit which arealso interchangeable terms used throughout the specification. The matrixfurther includes a low-profile additive, a cure initiator, a thickener,a process additive and a mold release agent. The additives include a UVinhibitor. The additional components are used to enhance theprocessability of the material and the performance of the lid. Less thanabout 30% of the fiberglass reinforced polymer matrix formulation is apetroleum based product comprising unsaturated polyester resin andthermoplastic additives, the remainder is inorganic or mineral fillerand reinforcing glass fibers chopped into, for example, one inchlengths. The mineral filler could include, for example, aluminatrihydrate, calcium carbonate, talc or clay. The polymer materialundergoes a cross linking reaction when cured under heat and pressure.Good heat resistance is a characteristic of all thermoset materials andthey differ from thermoplastic material in that once the compound curesinto a rigid solid it will not soften at elevated temperatures or becomebrittle at lower temperatures. The lid retains its original materialproperties and dimensional accuracy over a broad range of temperatures.UV resistance is optimized through a combination of using orthophthalicresin, polystyrene as the low profile additive for shrink control andalumina trihydrate filler to produce the best results againstweathering. A low level of organic material coupled with the use ofinorganic fillers, for example alumina trihydrate, results in thematerial being highly flame retardant. Using the UL Bulletin 94 protocolas a measure, the material performs at the highest possible 5Vflammability classification.

Referring to FIG. 2, the fiberglass reinforced polymer matrix ismanufactured as a continuous sheet 12. Mixed resin paste 14 istransferred to a doctor box 16 wherein it is deposited onto a movingcarrier film 18 passing directly beneath the doctor box. The doctor boxcontrols the amount of resin paste that is applied to the carrier film.Glass fiber rovings 20 are fed into a rotary cutter 22 above the resincovered carrier film. Chopped fiberglass fibers 24 are randomlydeposited onto the resin paste. The amount of chopped fiberglass that isdeposited is controlled by the cutter and the speed of the carrier film.Downstream of the chopping operation, a second carrier film 26 is alsocoated with resin paste 14 by a second doctor box 16 and is laid resinside down on top of the chopped fibers 24. This process creates a resinpaste and glass fiber sandwich which is then sent through a series ofcompaction rollers 28 wherein the glass fibers are wet out with theresin paste and the air is squeezed out of the sheet 12 to produce ahomogenous sheet of fiberglass and resin.

Before the fiberglass reinforced polymer matrix sheet can be used formolding it must mature. This maturing time is necessary to allow therelatively low viscosity resin to chemically thicken. The sheet is keptin a temperature room until the desired molding viscosity is reached.When the sheet is ready for molding it is cut into pieces of apredetermined size. As shown in FIG. 3 the cut pieces are then stackedand assembled into a charge pattern 30 that is the optimum shape andvolume to fill a mold cavity in a mold 31. The charge pattern is thenweighed for verification of correct charge weight. The preassembledcharge is then placed on heated mold surfaces 34 in a predeterminedlocation. The mold 31 is a matched set of machine steel dies comprisinga cavity die 32 and a core die 36. The mold cavity is positioned betweenthe cavity die and the core die.

The mold is heated, for example, by steam. After the charge is placed inthe mold cavity, the mold is closed and the charge is compressed. Thefiber reinforced polymer matrix material is a flowable compound andunder heat and pressure is transformed from a thick paste to a very lowand optimized viscosity liquid of viscoelastic state. The material flowsto fill the mold cavity. As seen in FIG. 4, the cavity die 32 and thecore die 36 are interfaced by a telescoping shear edge 38 which providesfor a gap between the core die and the cavity die to allow for the coredie to enter the cavity die. The telescoping shear edge allows for thematerial to be controlled during the molding or compression phase of theprocess. The clearance at the shear edge allows the escape of air aheadof the material flow front. The small clearance of the shear edge allowsair to pass but it is too small to allow an appreciable amount of thepolymer material to pass. The mold is held closed for a predeterminedamount of time to allow the cover to cure. After curing, the mold isopened and the cover is ejected from the mold surface of the core withthe use of integral ejector pins. The hot molded lid is placed into acooling rack and allowed to cool to room temperature before a machiningoperation.

Referring again to FIG. 3 the mold 31 includes an ejector system 40 forejecting the finished molded part. The mold can be made from A-36 toolsteel for example, however other materials could also be used. The coredie and cavity die are aligned by components in the tool, for instancealignment pins and bushings. Stop pads are utilized to control partthickness. As shown in FIG. 5, the core die and cavity die are providedwith a means to control the temperature of the blocks. For example asteam pot 41 can be incorporated. The temperature of the mold ismonitored by means of a thermocouple 42. The steam pot is a sealedcavity 44 which has internal supports 46 surrounded by an outerperimeter 48 and sealed with an additional plate 50 to maintain pressureand control the steam. A steam pot is utilized in both the core die andthe cavity die and allows steam to be used to provide a consistent anduniform heat transfer to the mold surfaces 34. The surface area of thesteam pot cavity allows for increased surface area for transfer asopposed to drilled lines. Other means to control the temperature of theblocks can include drilled holes or slots used with oil or electricalheating elements.

Referring to FIG. 6 the ejector system 40 includes ejector pins 52utilized to push the molded part off of the core die 36 at the end ofthe molding process. The ejector system includes an ejector plate 54which pushes a group of ejector pins that are flush with the top of thecore die or the bottom of the part lifted from the core die. The ejectorpins 52 are retained on the ejector plate 54 by means of a retainerplate 56 which has counter bored holes to capture the head of theejector pins. The ejector plate assembly is guided by means of guidepins 58 and bushings 60. The ejector plate is actuated by hydrauliccylinders 61 (FIG. 3) controlled by the molding cycle. Actuation of theejector plate can be achieved by other means such as chain poles orknockout bars in the apparatus. The ejector plate assembly is supportedby rails 62, support pillars 64 and a bottom plate 66. The ejector platealso has a provision for heating the mold with drilled holes for steam.

The top, bottom and sides of the mold assembly can be insulated tocontain the heat required for the process. It also insulates the heatfrom the machine or hydraulic press to manufacture the part.

Example Manufacturing Process for an Embodiment of the Invention Mixingand Storing Polymer Formulation

Ingredients Desired % Range Polyester Resin 23.25  10-40% Polystyrene(Shrink Control) 11.46   5-30% Catalyst 0.39 0.1-8% Inhibitor (PBQ) 0.260.1-8% Fiber Wetting Additive 0.35 0.1-8% Zinc Stearate (Mold Release)1.21 0.1-8% Inorganic Filler 24.99  15-50% Magnesium Oxide (Thickener)1.21 0.1-8% UV Stable Pigment (Gray) 1.89 0.1-10% Fiberglass (0.5″-2″Chopped) 35.0   5-60%

The polymer formulation is typed into an automated delivery system. Thissystem is responsible for mixing of all of the ingredients together,storing the polymer matrix and then delivering it to a compounder, forexample a Schmidt and Heinzmann (S&H) Compounder.

The formulation is mixed to ensure that the material is homogeneous.Controllers manipulate the order of addition, dwell time, blade speedand mixing temperature. Upon completion of paste matrix mixing cycle,several tests are performed to make certain the paste is correct beforebeing released to a holding tank. The holding tank's primary function isstorage. During the storing process, the paste matrix is agitated by lowshear mixing blades. If the weather is less than 65 F degrees a waterblanket is used to make sure that the paste does not lose temperature.This loss can influence the thickening response and negatively impactthe moldability of the material. The holding tank is placed on a scaleand is continuously metered gravimetrically to the compounder duringmanufacturing. The polymer matrix still does not have color or thethickener (polymer extender). Both of these ingredients are addedseparately to ensure that there is not any cross contamination in coloror troublesome thickening because of improper maintenance. The “b-stage”component is tested to confirm the desired formulation before it isreleased into production.

Batch mixing is typically used when formulation flexibility is required.When the lids are manufactured with one formulation, a continuousprocess can be employed. This allows the mixing process to be tailoredto one specific formulation. All of the ingredients are continuously fedto a mixer, typically an extruder. They are blended together in theextruder and introduced into the compounder. This process eliminates theadditional equipment needed to feed and mix the b-side.

Matrix and B-Stage Delivery

The automated delivery system will determine pump rates needed formanufacturing. This system will determine the amount of paste deliveredper hour to the compounder based on the matrix specific gravity, productweight, glass percent and sheet weight. The matrix and b-side arecombined by running through a series of high shear cowls type mixingblades or a static mixer. The mixed material is then stored in a surgetank and delivered to the compounder with stater pumps. Inside of thedoctor blades on the compounder are height sensors. The height of thematerial in the doctor boxes is controlled by the automated deliverysystem.

Compounding

There are many variable that can be changed on the compounding machinesuch as:

TABLE 1 Preferred Values Range MACHINE Belt Speed 5 m/min 3-20 m/minCutter Speed 167 RPM 100-668 rpm Feed Roller 2.5 Bars 1-5 bar Rubberroll3.5 Bars 1-5 bar Oscillation 2.0 Bars 1-5 bar Winding Counter 250100-300 rpm Holding Tank Temperature 95 F. ± 5 F. 60-120 F. Final MixerTank Temperature 95 F. ± 5 F. 60-120 F. DOCTOR BOXES Lower Dam Height0.069″ 0.050″-0.120″ Upper Dam Height 0.069″ 0.050″-0.120″ Dam SidesHeight 0.065″ 0.020″-0.100″ Level SP #1 38 mm 20-80 mm Level SP #2 38 mm20-80 mm POLY FILM Upper Film Tension 6.0 Bars 2-10 bar Lower FilmTension 6.0 Bars 2-10 bar Sheet Width 34½″ 10″-80″ Deflector Width 35⅛″8″-82″ COMPACTION UNIT Belt Tension (Upper) 4 Bars 2-10 bar Belt Tension(Lower) 4 Bars 2-10 bar Impregnation Bridge Lower Range 9.5 Bars 4-12bar Turret Winder 4 Bars 2-8 bar Smoothing Roller Up/Down UP up/down

Since the specific gravity of the material is known, the height of thedoctor blades can be determined based on the product weight of thematerial. The product weight of the compound is measured by the weightper unit area. Typically weight is measured in grams/ft². The fiberglasscomponent can also be measured. Varying the RPMs of the chopper willlinearly change with the weight of the fiberglass. The product weight ofcompound is 545 g/ft.².

Paste samples (matrix and b-side together) are taken throughout the runand measured with a viscosmeter. Typical measurements are takeninitially, at 24 hours and at 36-60 hours. Several variables areconsidered when determining the thickening curve: temperature, initialviscosity and molding viscosity. These values are optimized based off ofprior compounding and material trials. When lot number of either theresin or the thickener change, a thickening study is run to determine ifthe levels need to be changed. The target molding viscosity of thematerial is between 20-45 MM cps. Viscosity measurements are taken witha Brookfield DV-II.

After the polymer matrix is introduced to the fiberglass the sheet isthen squeezed together between serpentine rollers to wet-out thefiberglass. Since this process yields structural parts, a ft² templateis used to cut a sample of the material. If it falls within apredetermined range, the material is qualified for release.

The product weight samples are collected and used to mold lab panels.During the molding a sensor detects the dielectric properties of thematerial and determines the gel and cure time of the material. The curedpanels are then cut up into various samples for testing. Typical testingincludes tensile strength, flexural strength, specific gravity,fiberglass content and water absorption.

TABLE 2 Physical properties measured on 0.120″ thick panel molded 24Hrs. after manufacture. Molding Conditions: 3 min. at 330° F. MoldingPressure = 200 psi. Coverage = 60% Property (units) Desired Range GelTime (s) 35-50 Cure Time (s)  87-105 Product Weight (g/ft²) 534-556Specific Gravity (g · cm⁻³) 1.63-1.67 D3 to D5 Viscosity (Cps) 23-35Tensile Strength (psi) 15,700-18,300 Flexural Strength (psi)26,000-31,500

Once the material has reached the predetermined values of the qualitytesting, the material is released into production.

Molding Process FRPM

-   -   The fiber reinforced polymer matrix (FRPM) Compound is delivered        to a self aligning actuating mold (SAAM) area on roller carts        that hold (8) rolls of compound weighing approximately 200-500        lbs. each, or in a box with 500-6000 lbs.    -   Each roll has a tag that identifies Manufacture Date,        Formulation, Batch #, Roll# and Weight. Material is not released        until it has passed all QC requirements as detailed in the        Compounding section.    -   The carts are staged at the FRPM Cutting area where the        automated slitter is located.    -   The SAAM Production Molding Operation Notebook is referenced        which shows the charge size and weight for the particular lid        that is to be molded.    -   Once the sheet is located the correct cut sheet and the slitter        is set to automatically cut the charge to size and de-film the        compound.    -   The cut charge sheets are then weighed to the correct charge        weight and stacked in completed individual charge packs ready to        manufacture.

SAAM PRESS

-   -   A SAAM system enables large platen area presses to be designed &        installed without the need of installation pits. Other press        types are also applicable.    -   The use of a self aligning press was accomplished by inverting        the hydraulic cylinders that supply the pressing tonnage.    -   The use of a self aligning press also allows for any change in        location of the press, to meet any change in production demands,        to be carried out with a minimum of disruption to the production        facility.    -   To support the SAAM production molding system a special Low        Pressure Molding

Compound (LPMC) was developed and FRPM (Fiber Reinforced PolymerMaterial) is a form of LPMC.

-   -   The Platen SAAM system allows for the interchange of steel tools        (molds) in the normal way.    -   The tools at present are as follows:    -   15″ round (1400)    -   13″×24″ lid mold (1324)    -   17″×30″ lid mold (1730)    -   24″×36″ lid mold (2436)    -   24″×48″ lid mold (2448)    -   Split 30″×48″ lid mold (3048)    -   Typical SAAM Operating Pressures: 3,000 psi    -   Cylinder bore: 12 inch    -   Rod diameter: 5.5 inch    -   Effective area of cylinder: 89.34 square inches    -   At 3,000 psi hydraulic pressure the cylinder develops 268,017        lbs. of force    -   Therefore, four (4) cylinders develop 1,072,068 total lbs./536        tons of force    -   A 17″×30″ lid has a plan view surface area of 17″×30″: 510        square inches    -   1,072,068 lbs. of force divided by 510 square inches equals        2,102 psi molding pressure    -   A 24″×36″ lid has a plan view surface area of 24″×36″: 864        square inches    -   1,072,068 lbs. of force divided by 864 square inches equals        1,241 psi molding pressure    -   A 24″×30″ lid has a plan view surface area of 24″×30″: 720        square inches    -   1,072,068 lbs. of force divided by 720 square inches equals        1,489 psi molding pressure.    -   The molding pressures get halved when molding two-up in the same        SAAM.    -   The plan view surface area is smaller than the total surface        area so when using the plan view area around 400 psi molding        pressure is utilized.

Molding Procedures

-   -   The press is preheated to ensure the proper settings.    -   A notebook of Master Control Settings is consulted for the sheet        for the particular lid to be molded and screens 1 and 2 are set        to the proper Control Settings. This Master Control Settings        Record Sheet shows proper setting for each of the following:

Value Range SCREEN 1 1. Open Position 52″ 42″-60″ 2. Load Position 42″35″-52″ 3. Slow Down Position 34″ 33″-35″ 4. Closed Position   31.5″32″-25″ 5. Cure Time 400 sec. 150-600 sec. 6. Fast Speed 0.8 IPS 0.1-1.0IPS 7. Slow Speed 0.2 IPS 0.1-1.0 IPS SCREEN 2 1. Top Poppet Auto Time50 sec. 0-100 sec. 2. Bottom Poppet Auto Time 50 sec. 0-100 sec. 3. TopPoppet Manual Time 10 sec. 0-100 sec. 4. Bottom Poppet Manual Time 15sec. 0-100 sec. 5. Ejection Time 25 sec. 0-100 sec. 6. Maximum Slow CureTime 99 sec. 0-100 sec.

-   -   The operator reviews the temperature indicators on the master        Control panel to see if the molds are up to the proper        temperatures, 325° F.-270° F. for upper tools and 320°        F.-265° F. for lower tools.    -   Once the screens are checked the operator take a hand held        temperature gauge and verifies that the mold temperatures match        the screen readings from the thermocouples. He is also verifying        that the upper mold is always hotter than the lower mold to        avert any telescoping shear edge mold crash.    -   Once the temperatures are verified the operator then visually        inspects the mold surfaces for cleanliness and any sign of        debris or scumming. If any is seen it is removed with brass        tools and air streams.    -   The press is then set into Automatic mode and readied for the        molding of the first part.

Molding Operation

-   -   The delivered charges are inspected and measured to ensure they        are the correct size and weight. The first charge is staged on        the scale and the weight is noted. On the PROCESS DATA        &PARAMETERS MASTER CONTROL SETTINGS RECORD SHEET there is a        heading “CHARGE DIMENSIONS”. Under this headings are the        following line items that contain the proper information        regarding the charge for example, a 17×30 (1730) charge:

Value Range 1. Weight LBS.: 26.1 lb 26.1-26.6 lbs 2. DIMENSIONS: 28.5″ ×16″ 16″-30″ × 8″-17″ 3. NUMBER OF LAYERS: 8 5-15

-   -   Once the charge has been confirmed to meet specification, the        green “CYCLE START” button is pushed to activate the automatic        molding cycle and the mold lowers to LOAD POSITION.    -   Once the mold stops to the load position, the charge is        delivered into the mold via a loading device and the charge is        precisely position on the lower mold being centered in each        direction.    -   As soon as the loading tool has exited the mold parameters, the        operator again pushes the green “CYCLE START” button and the        press lowers from “SLOW DOWN POSITION” to “CLOSED POSITION”.        Once the presses sensors confirm that each corner is at Full        Closed position, the “CURE TIME” cycle starts.    -   As the automated cycle starts the operator inspects and places        the next charge onto the scale again verifying the weight.    -   After the CURE TIME cycle is completed, the air poppet is        automatically activated and the press opens to SLOW SPEED        position and then opens to FAST SPEED and returns to the OPEN        POSITION setting of the cycle.    -   As the press is opening to OPEN POSITION and the mold has        cleared the full extension dimension of the ejector pins and        reaches a preset clearance height, the ejector system is        activated and the part is raised above the lower mold surface to        the full height of the ejection pins.    -   As soon as the ejectors have reached full height, the Unload        Tool is inserted under the part and the ejector rods are        automatically lowered.    -   Once the ejectors are back in full rest position, the Unload        Tools is extended to the front of the press and the part is        delivered to the operator to do a visual inspection, deflash the        edges and place in the cooling cart.    -   Once the part and the Unloading Tool have been removed from the        press parameters, the operator visually inspects the mold        surfaces and clears and debris with an air stream. The cycle        begins all over repeating each of the documented steps.

Machining

-   -   Each Cooling Cart handles multiple parts. As the carts are        filled they are removed from the SAAM area and placed in a        staging area to cool and stabilize. During this period the parts        are randomly inspected by QC and verified to meet quality        specifications dimensionally, weight and appearance.    -   The parts need to cool to less than 150° F. prior to any        machining being done to the part. This cooling process ensures        the dimensional stability and flatness of the part prior to        machining.    -   The machining operator will go through the start-up checklist        contained in the computer numerical controlled (CNC) Operations        manual and once the checklist is complete he will set the        machine to the appropriate machining program corresponding to        the sized lids being machining.    -   The CNC has been programmed to machine one part at a time. Each        lid has its own program.    -   The operator removes a part from a cooling cart and places it in        the designated position for the machining cycle.    -   Once the part is positioned the operator will activate the        vacuum holding the part in proper position. The Operator pushes        the Green Cycle Start button and the CNC verifies that the        vacuum is activated and then moves from the center home position        to verify the part is in proper position, once verified by the        machine, it will automatically start machining the part on the        outboard end of the CNC bed.    -   As this machining is done the operator will position the next        part into its position on the Inboard end of the CNC bed.    -   Once the machining is complete the CNC will return to the Center        Rest position and release the vacuum on the completed part. The        operator will again activate the vacuum on the next part and        then push the green Cycle Start button.    -   During machining the operator will remove the previously        machined part, do a visual inspection, wiped down, blow off and        place on a pallet for shipping for final assembly.

Referring again FIG. 1, the lid or cover 10 includes an uppermostsurface 70 which is substantially flat and when installed on a vault orpit 72 is even with grade level surface. As shown in FIG. 8, the bottomside 74 has an outer rim 76 around the perimeter of the lid with arecessed interior area or cavity 78. The cavity has features 80 and 82to allow for the attachment of accessories to be discussed in moredetail subsequently herein and thru-holes 84 for attachment to the vault72. A plurality of continuous support ribs 86 extend from opposite sidesof the outer rim within the cavity. The support ribs are spaced totransfer load and minimize deflection of the lid under load to the outerrim. As shown in FIG. 9 the outer rim is supported by a ledge 88 in theouter walls 90 of the vault 72. Although the lid is shown as beingsupported by a ledge 88 in the walls of the vault, other types ofsupporting recesses of the vault are contemplated to support the lid.

The ribs 86, for example three, extend uninterrupted laterally to spanthe cavity between opposite sides of the perimeter of the rim. As shownin FIG. 10 alternative designs were tested to determine the effect ofadditional supporting structures within the cavity 92 of the lid 94. Theribs 86 (as shown in FIG. 8) were superior to alternative designs whichincorporates intersecting ribs 96 extending the length or portions ofthe cavity. The lid of FIG. 10 also incorporated intersecting hubs 98and it was shown through testing that ribs 86 alone improve the loadcarrying capability and therefore intersecting ribs 96 and hubs 98 areunnecessary. The test results as shown in Table 3 illustrate the liddesign as shown in FIG. 8 comprising a polymer material as disclosedherein produced a larger load carrying capability when the intersectingribs 96, hubs 98 and small ribs 100 were removed.

TABLE 3 Nominal Load to First Nominal Structural Defect Load FailureVersion Pounds Force Pounds Force 1730 with Intersecting Ribs 22,00029,000 1730 with Laterally 30,000 31,000 Uninterrupted Ribs 1730 withLaterally 33,700 39,000 Uninterrupted Added Depth Ribs

In addition deeper ribs 86 as shown in FIG. 11 produced the largest loadcarrying capability. Ribs 86 also can have a curved outer radius 102allowing the rib to have a height in the center taller than at thejuncture with the outer rim.

As shown in FIGS. 12 and 13, the top surface 70 includes a texturedsurface 104 or surface condition created by a pattern of features atdifferent depths in the mold surface. The textured surface 104 includesa change of depth of the flat surface which creates a slight protrusion105 into the surface to push the glass fibers 24 of the material awayfrom the surface creating a resin rich surface 107 during molding.Having the glass fibers 24 away from the textured surface adds to thelong term weatherability of the lid. The textured surface is, forexample, a Corinthian texture. The combination of the texture and the UVstability achieves a delta E values of less than 9.0 when exposed for5000 hours using the SAE J2527 test.

The top surface 70 also includes a series of bosses 106 of varyingheights to create a gripping surface. The bosses 106 are molded atvarious heights to allow for aggressive transitions in the surface ofthe lid. The bosses are arranged in a pattern of alternating groupswhich allows for additional edge surfaces to grip moving surfaces, suchas vehicle tires, which may come in contact with the top of the lid. Thebosses create more surface area for flexible materials to come incontact with. The result of the bosses is the surface allows the lid tomeet slip resistance requirements. Although FIG. 12 illustrates a bosspattern of alternating series of three bars having rounded ends, it isto be understood that other geometrical shapes and sizes andarrangements are possible to create the necessary tread pattern or slipresistance surfaces. Other testing requirements the lid of the presentinvention meets are as follows:

Polymer lid Related Specifications:

The lid is tested to industry recognized standards for:

-   -   Chemical Resistance Per: Telcordia R3-14 and ASTM D543-06    -   Ultra Violet Exposure Per: ASTM G154    -   Fungus Resistance Per: ASTM G21    -   Flammability Per: UL 94-5 VA and ASTM D635-06    -   Water Absorption Per: ASTM D570-05

The lid is tested to industry recognized standards for:

-   -   AS 4586: 2013 Slip resistance classification of new pedestrian        surface materials—Appendix A.    -   ANSI/SCTE 77-2010 Specification for Underground Enclosure        Integrity, SCTE, 2010    -   GR-902-CORE, Generic Requirements for Handholes and Other        Below-Ground Splice Vaults, Telcordia, 2013    -   ASTM C857-11, Standard Practice for Minimum Structural Design        Loading For Underground Precast Concrete Utility Structures,        ASTM, 2011    -   AS 3996 2006, Access Covers and Grates    -   BS EN 124:1994 Incorporating Amendment No. 1 Gully Tops and        manhole tops for vehicular and pedestrian areas—Design        requirements, type testing, marking, quality control

As shown in FIG. 1 the top surface 70 has a recess 108 for theattachment of an identifying component 109 such as an ownership markeras shown in FIG. 14. The ownership marker would have a post extendinginto hole 110. The identifying marker could be removed and exchanged incase of change of ownership of the lid.

Referring again to FIG. 1 the lid includes holes 112 and 114 extendingthrough the lid to allow for either bolt down or captive locking optionsto attach the lid to the vault. As shown in FIG. 14 either an L-bolt116, or alternatively a thru-bolt 118 passes through either hole 112 or114 and would be rotated to engage a groove 120 positioned in the wall90 of the vault as shown in FIG. 15. The L-bolt 116 is retained within ahousing 122 attached to fastening feature 82 positioned on the bottomside of the lid. As shown in FIG. 16, a flange 124 would be attached tofastening surfaces 80 which would engage a groove 126 in the wall 90 ofthe vault.

Other types of fastening mechanisms can be utilized in addition to theL-bolt construction as identified in Applicant's U.S. Pat. No.7,547,051, the contents of which are incorporated herein by reference inits entirety. Such as, for example, the lid could utilize aself-latching and locking assembly 127 for attachment of the lid to thevault as shown in FIG. 17 and illustrated in detail in Applicant's U.S.Pat. No. 8,220,298, the contents of which are incorporated herein byreference. Any unused holes 112, 114 not utilized for a particularattachment system can be closed with a removable plug 130 (FIG. 14)which at any time could be removed for the incorporation of a differentsecuring option.

As shown in FIG. 1 the lid includes a pick hole 132 for lifting the lidoff of the vault. As shown in FIG. 18 a pick hole retaining cup 134(also shown in FIG. 8) is positioned within the pick hole 132 which hasa rod 136 positioned in a recess across the opening which can be engagedby a hook to lift the lid off of the vault. As shown in FIG. 14 the lidincludes a pick hole cap 138 to prevent debris from collecting withinthe pick hole during use. Further specifics and features of the pickhole retaining cup for lifting the lid off of the vault is illustratedin Applicant's U.S. Pat. No. 8,708,183, the entire contents of which areincorporated herein by reference.

As shown in FIG. 19, the molding and machining operations can beautomated through the use of robotics 140. A robot 142 having aprogrammable logic controller would move from a neutral position to acharge loading station 144 where an operator would load a charge pattern146 onto a loader 148 positioned on an end of an arm 150 of the robot.The programmable logic controller of the robot then moves the loader tothe neutral position facing the mold press 31. The robot waits in theneutral position until the mold press opens and the controller makessure the parts are clear and the ejection apparatus of the mold isretracted. The robot then moves to the open press and positions thecharge loader 148 into the cavity 43 of the mold 31. The controlleractivates the loader dropping the charge into the mold cavity andretracts the loader from the mold.

Upon completion of the molding process and ejection of the molded coverfrom the mold, the robot includes a retractor 152 comprising a plate 154and series of suction cups 156. The controller opens the press at thecorrect cycle time and activates the cover ejection mechanism whereinthe robot positions the retractor 152 over the molded cover so that thesuction cups 156 can engage the cover and move the molded cover to aconveyor system 158 and releases the cover onto the conveyor system. Theconveyor system then delivers the molded cover to a machining station160 which includes a plurality of rotating brushes 162 to deburr themolded cover. The machining station also includes drilling holes for thevault attachment mechanisms.

Final assembly of the cover includes placing the pick hole rod in therecess of the pick hole cup and securing the cup and cap to the lid,securing the identification marker to the lid, securing the L-bolt,through bolt or self-latching mechanism along with the retaining flangeand plugging the holes with caps for the attachment mechanisms not used.

Although the invention has been described and illustrated with respectto various embodiments herein, it is to be understood that changes andmodifications can be made therein which are within the full intendedscope of the invention as hereinafter claimed.

What is claimed is:
 1. A method of manufacturing a fiber reinforcedpolymer material lid for an utility vault comprising the steps of:mixing an unsaturated polyester thermosetting material into a resinpaste; compounding the paste into a fiber reinforced composite materialsheet; maturing the compounded fiber reinforced composite materialsheet; cutting the matured compound sheet into a charge pattern; moldingthe charge pattern in a mold cavity of a heated mold under low pressureto form the lid; and cooling and machining the lid.
 2. The method ofclaim 1 wherein the mixing step comprises combining polyester resin,polystyrene, a catalyst, a UV inhibitor, a fiber wetting additive, amold release agent and an inorganic or mineral filler.
 3. The method ofclaim 2 further comprising adding a thickener and a color pigment. 4.The method of claim 1 wherein the compounding step includes:transferring the resin paste to a first doctor box and a second doctorbox; depositing a first layer of resin paste from the first doctor boxonto a first carrier film; depositing reinforcing fibers onto the firstlayer of resin paste on the first carrier film; depositing a secondlayer of resin paste from the second doctor box onto a second carrierfilm; layering the second layer of resin paste on top of the first layerof resin paste containing the reinforcing fibers; and compacting thefirst layer of resin paste, reinforcing fibers and second layer of resinpaste to form a sheet.
 5. The method of claim 1 wherein the maturingstep comprises chemically thickening the sheet.
 6. The method of claim 1wherein the molding step comprises the steps of: compressing the chargepattern in the mold; transforming the charge pattern from a resin pasteinto a viscoelastie liquid; filling the mold cavity with theviscoelastic liquid; evacuating air from the mold cavity; and curing thelow viscosity liquid in the mold cavity under heat and low pressure. 7.The method of claim 1 wherein the resin matrix paste comprises about 10%to about 40% polyester resin.
 8. The method of claim 1 wherein the resinmatrix paste comprises about 5% to about 30% polystyrene.
 9. The methodof claim 1 wherein the resin matrix paste comprises about 15% to about50% inorganic or mineral filler.
 10. The method of claim 1 wherein thecompounded fiber reinforced composite material comprises about 5% toabout 60% fiber glass.
 11. The method of claim 1 further comprising thestep of automatically loading the charge pattern into the mold cavityand removing the molded lid and moving the molded lid to a machiningstation.
 12. The method of claim 11 wherein the step of automaticallyloading the charge pattern and removing the molded lid and moving themolded lid is by a robot.
 13. A mold for molding a fiber reinforcedpolymer material utility vault lid comprising: a cavity die; a core diehaving a telescoping shear edge for interfacing the core die within thecavity die, wherein the lid is molded between the cavity die and thecore die; and a lid ejection mechanism for removing the molded lid fromthe mold.
 14. The mold of claim 13 further comprising means for aligningthe cavity die and the core die.
 15. The mold of claim 14 wherein themeans for aligning are alignment pins and bushings.
 16. The mold ofclaim 13 wherein the telescoped shear edge provides for a gap betweenthe core die and the cavity die to allow air to escape during a moldingperiod.
 17. The mold of claim 13 further comprising means to heat andcontrol temperature of the cavity die and the core die.
 18. The mold ofclaim 17 wherein the means to heat and control temperature is a steampot including internal supports and a sealing plate.
 19. The mold ofclaim 13 wherein the lid ejection mechanism are pins extending throughthe die core and actuated by a pin plate.
 20. The mold of claim 19wherein the pin plate is hydraulically actuated.
 21. The mold of claim19 wherein the pin plate is mechanically actuated.
 22. The mold of claim13 wherein the cavity die has at least one textured surface.
 23. Themold of claim 22 wherein the textured surface is a corinthian texture.24. The mold of claim 13 where the die cavity die has recesses forforming bosses on an upper surface of the lid.
 25. The mold of claim 24wherein the recesses are of varying depths.